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Property and Equipment, Net (Detail) - USD ($)
$ in Millions
3 Months Ended 9 Months Ended
Oct. 31, 2018
Oct. 31, 2017
Oct. 31, 2018
Oct. 31, 2017
Property, Plant and Equipment [Abstract]        
Depreciation expense $ 38 $ 30 $ 107 $ 85
Interest costs capitalized to property and equipment $ 3 $ 3 $ 7 $ 6